Fw-190: the roots of the great roll rate?

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Do you have evidence of that?
 


You may notice that the rear "spar" on this more accurate drawing is hardly more than a very thin aluminium piece, sufficient to attach control surfaces to. Compare it to the actual main spar, which was massive piece of entirely different construction.

That, plus the fact that the aircraft had a rather low aileron revarsal speed due to wing twist, as noted in NACA 868. This indicates lack of stiffness, which is logical if all your main load bearing elements are in/very near to the leading edge of the wing (i.e. the main spar and the D-box) and you have next to nothing in the back. The wing could handle normal accelerations well, but not wing twist.
 

Your basing this on what you see on the drawing. Do you have a size of the rear spar? I know many aircraft whos main spar is no thicker than .030, but when built up into the wing with a spar cap carries a good portion of the load. If there is supporting structure attached to it, it is obvious if carries a load. It is also obvious that it is NOT the primary load carrying structure of the wing, but it does carry a load and by all accounts, it is a "spar" by definition.
 
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Definition by whom?-and why were all other wings (eg at German, Bf 109) with the same construction named one spar wing. Being confused now.
Cimmex
 

Yes I was going by this drawing. I also think that we basically agree with you - what I meant that it is not a primary load carryinng element in the wing, which is my definition for a two spar design, where both spars contribute to a significant amount to the load carrying. Of course the rear spar also carries some of the load, but my guess that this contribution is not significant, since in these WW2 fighters this is also true to just about any part of the structure. The skin, ribs etc. also carried loads. In short, we seem to argue semantics.
 
cimmex said:
Definition by whom?-and why were all other wings (eg at German, Bf 109) with the same construction named one spar wing. Being confused now.
Cimmex
Click to expand...

I could name at least 2 dozen books such as "Stick and Rudder" (Wolfgang Langewiesche) FAA Advisory Circular AC43.13, Aircraft Structures for Engineering Students (Cutler) that defines a "spar" as (in so many words) "A structural member of the wing, running spanwise at right angles to the fuselage." Some German engineers may have thought that because ONE spar carried the main load the wing in question had ONE spar.
 
Agree as well. Bottom line, there is NOT one spar in a Spitfire wing. One spar may carry the majority of the load, but by basic definition, the wing has two spars.
 
Tante Ju said:
You may notice that the rear "spar" on this more accurate drawing is hardly more than a very thin aluminium piece, sufficient to attach control surfaces to.
Click to expand...
It's also substantial enough for the rear of every wing rib to be attached to it, and the wing covering to be rivetted to it, as well. Your "very thin aluminium piece" was strong enough to remain rigid, and hold the flaps and ailerons in place, without bending, or causing them to bind. It helped the wing to retain its integrity so that it could turn inside the 190 109, and still have the gentle stall warning so beloved by Spitfire pilots.
 
Probably not in WW II fighters although some one may find one. Some light planes use a "false" spar to hang ailerons and/or flaps from. The false spar may run across a number of ribs but is not connected to the fuselage or loads are not carried into/through the fuselage.

This may be the dividing point. The main spar may handle 51-99% of the load with the "rear" spar handling 49-1% of the load. Without knowing the designers intent or calculations (wing rib numbers/strength/spacing + wing skin strength + any spanwise stringers + any cross braces it is a little hard to figure out just what the rear spar is doing on most aircraft. If it is connected to a fuselage frame or carried through to the other side you have to assume it is doing something. If it stops at the wing root fillet or before then you can assume it is just a mounting point for movable surfaces although it may help resist twisting a bit.

Trying to eyeball load carrying ability from a small two dimensional sketch and reach a valid conclusion in 3 dimensional reality is almost impossible.

Which can carry more load or resist twisting better a 1 x 4 X 12 ft piece of wood or a 1 x 6 x 12 ft piece of wood. Both look the same from the top.
 
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Afaik the Ta 152, both short and long wrong versions, had a shortened front wing spar (to accommodate additional fuel tanks? ) afaik. Wonder if with this new wing structure the Tas (short wing) could retain the roll rate.
The late Doras were supposed to have the original fuel tank also, but I've seen an illustration with these tank together with the normal long front spar.
 
Take your time to discern the rear spar in the upper picture. In the meantime, the main spar seem like a bulletproof item ,at least the upper lower beams.

 
As I have understood it, at least in late 30s and early 40s single spar design meant a wing which main torsional box was formed by a heavy main/front spar and the skin between it and the leading edge and in a two spar wing the main torsional box was formed by a front and a rear spars and the skins between them. Look Morgan's and Shacklady's or Price's Spitfire books, IIRC in those they say that Spitfire had a single spar wing, and at least here in Finland we say that 109 also had single spar wing even if both had a lighter rear spar.

Juha
 
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Hello Edgar
an excellent photo, it also shows the normal situation in the photos on the structure of Spit's wing, one can see the inner structure of the wing behind the main spar but not inside the D shaped torsional box which integrity was weakened only by a few handholes and the holes for the muzzles and barrels of the armament.

Juha
 
GregP said:
I have never seen any report claiming the Hellcat and Corsair could roll with an Fw 190, but have seen MANY rep[orts claiming the Fw 190 was superior at roll to everything it came against.

Maybe a link to the report in question so we can read it?
Click to expand...

As is so often the case, I can't find it! But its a fairly well known flight comparison - can anyone else help.
My recollection is that the 190 was a Fw190A-5 paseed on by the British. It was found to be a bit better than the Hellcat and bout equal to the Corsair, althogh all the pilots said they would refer the American fighters in actual combat. Both outurned the 190 easily and matched it in roll rate though the 190 was praised for the ease whith wich it rolled in either direction. The 190 generally outclimbed and out accellerated the F4F.
 
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